1. Filed of the Invention
The present invention relates to a method wherein a specimen, such as blood, is pipetted into a mixing cell and is allowed to react with a reagent to thereby analyze a component thereof.
2. Discussion of the Background Art
Operations for pipetting specimens and reagents into reactors have been mechanized in order to prevent scatter from worker to worker, to save personnel expenses, to shorten the assay time, etc. Since these pipetting apparatuses are very expensive, it has been typical practice to employ a single apparatus for plural purposes even when plural types of reagents are employed.
To simplify such a pipetting apparatus, and to avoid contamination of reagents with each other, JP-A-8-122336 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses an assay method wherein a pipetting tip (which is called a pipette in this document) is employed with the use of a cartridge provided with a well for optical measurement (hereinafter referred to as a xe2x80x9cmeasurement cellxe2x80x9d), a holding member for holding the pipetting tip and another well in which a washing liquor is to be contained (hereinafter referred to as a xe2x80x9cwashing liquor cellxe2x80x9d).
The above-described cartridge is employed when a specimen (blood, body fluid, etc.) is pipetted into the mixing cell in a definite amount either directly or after diluting with a liquid diluent contained in the dilution cell, and a reagent contained in the liquid reagent cell is collected in a definite amount and is discharged into the above-described mixing cell to which the specimen has been already added, thereby initiating the assay.
In the cartridge as described above, a single pipette is used in all of the operations of pipetting and diluting the specimen, pipetting the liquid reagent, pipetting the washing liquor, etc. Although these pipetting operations are carried out by using a single pipette, there arises no contamination. This is because the pipetting tip is washed with the washing liquor preliminarily supplied into the washing liquor cell. This washing liquor cell also serves as a waste liquor cell containing the waste liquor after washing. So long as there arises no trouble of contamination, it is advantageous to carry out all of these pipetting operations with the use of a single pipette. These advantage arise because it is unnecessary in this apparatus to exchange pipetting tips frequently, or to provide a member for washing the tip, as in the conventional cases and, thus, the assay apparatus size can be reduced.
As in the assay method disclosed by JP-A-8-122336 described above, it has been a common practice that a pipetting tip contained in a cartridge is set to a nozzle immediately after the initiation of the assay and the first specimen, liquid reagent or the like is sucked thereby. In most cases, the first specimen, liquid reagent, or the like, is sucked without effecting any pretreatment. Typically, the inside of the pipetting tip is treated with silicone, etc. to thereby discharge all of the collected liquid. When a liquid having a low viscosity is collected, the liquid can be sufficiently discharged from the pipetting tip without remaining therein and, thus, the liquid collection can be performed at a high accuracy.
However, the cartridge disclosed in JP-A-8-12233 must be provided with exclusive washing liquor cells for containing washing liquor for washing the pipetting tip. Since insufficient washing causes contamination, the washing should be carried out at least to such an extent that avoids contamination. Therefore, a plural number of washing liquor cells are necessary. As a result, the cartridge is enlarged and the performance is worsened.
As described above, it is unavoidable to use a new pipetting tip immediately after the initiation of the assay. When a highly viscous liquid (such as whole blood, etc.) is sucked, the volume of the sucked specimen varies even though the interior of the pipetting tip has been treated with silicone as described above. As a result, there arise errors in the assay data. This is apparently because whole blood has both of hydrophilic and hydrophobic natures, but the pipetting tip exhibits a highly hydrophobic nature that brings about strong resistance in the course of sucking. The viscosity might also affect this phenomenon.
An object of the present invention is to provide an assay method whereby a tip can be washed without providing any cell exclusively for washing.
Another object of the present invention is to provide an assay method whereby a liquid can be accurately collected in a definite amount by using a pipetting tip.
These and other objects of the present invention has been achieved by a method of assaying a specimen, comprising:
preparing (i) a specimen, (ii) a liquid cell in which a liquid used for assaying a component in the specimen is to be contained, and (iii) a mixing cell wherein the specimen and the liquid are mixed;
supplying a liquid reagent into the liquid reagent cell in an amount exceeding the amount required in the assay;
pipetting a portion of the specimen and a portion of the liquid into the mixing cell using a pipetting tip; and
washing the pipetting tip with the liquid remaining in the liquid cell.
Moreover, these and other objects of the present invention has been achieved by a method of assaying a specimen, comprising:
preparing (i) a specimen, (ii) a liquid reagent cell in which a liquid reagent is to be contained and a liquid diluent in which a liquid diluent is to be contained, and (iii) a mixing cell wherein the specimen and the liquid reagent are mixed;
supplying a liquid reagent and a liquid diluent respectively into the liquid reagent cell and the liquid diluent in respective amounts each exceeding the amount required in the assay; and
pipetting a portion of the specimen, a portion of the liquid reagent and a portion of the liquid diluent into the mixing cell using a pipetting tip; and
the method further comprising at least one step of:
washing the pipetting tip with the liquid remaining in the liquid reagent cell, and
washing the pipetting tip with the liquid remaining in the liquid diluent cell.